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Full text of "Kesterson Reservoir 1990 site management plan"

SJVDP HRPARV (nrD'J 



LIBRARY COPY 

SAN JOAQUIN VALLEY 
DRAINACF PROGRAM 



KESTERSON RESERVOIR 
1990 SITE MANAGEMENT PLAN 



March 1990 



KESTERSON RESERVOIR 
1990 SITE MANAGEMENT PLAN 



March 1990 



KESTERSON RESERVOIR 
1990 SITE MANAGEMENT PLAN 



INTRODUCTION AND PURPOSE 

The purpose of this document is to present the Site Management 
Plan for Kesterson Reservoir for 1990. This document describes 
actions taken to date, current conditions at the Kesterson 
Reservoir, and plans for further actions. 

ACTIONS COMPLETED 

The Department of Interior (Department) has completed two major 
actions with respect to cleanup of Kesterson Reservoir. These 
are: termination of subsurface agricultural drainage water flow 
into Kesterson Reservoir; and filling of potential ephemeral pool 
areas in the Reservoir with soil. In addition, the Bureau of 
Reclamation (Reclamation) has actively managed Kesterson 
Reservoir since the completion of filling to minimize potential 
impacts to wildlife and ground or surface waters from selenium 
contamination. 

Termination of Subsurface Agricultural Drainage Water Flow 

The source of contamination at Kesterson Reservoir was irrigated 
agricultural tile drainage water carried to the Reservoir via the 
San Luis Drain (SLD). On April 3, 1985, the Department entered 
into an agreement with Westlands Water District to curtail 
drainwater discharges to the SLD. Drainwater discharge to the 
SLD was discontinued entirely by June 30, 1986. Since August 
1986 when drainwater remaining in the SLD quit flowing into the 
Reservoir, no drainwater has been discharged to Kesterson 
Reservoir. Hence, since that time, there has been no further 
input of drainwater contaminants to Kesterson Reservoir. Due to 
the natural geochemistry of the ground-water aquifer beneath 
Kesterson Reservoir, termination of drainwater discharge to 
Kesterson Reservoir essentially eliminated the threat of further 
selenium contamination of the ground-water aquifer. 

Filling of Kesterson Reservoir Ephemeral Pools i 

Monitoring conducted at Kesterson Reservoir demonstrated that 
residual contamination had manifested itself in significant 
wildlife impacts primarily through the aquatic food chain. In 
order to eliminate this exposure pathway, Reclamation dewatered 
the Reservoir ponds and filled low-lying areas (ephemeral pools) 
of the Reservoir with 1,050,437 cubic yards of material in 1988. 
These actions have essentially eliminated aquatic habitat at the 
Reservoir and, thus, broken the food chain through which aquatic 
wildlife impacts were manifested in the past. 



1989 Management Actions 

Management actions completed during 1989 focused on areas where 
rainwater puddled during the winter of 1988-1989, and on 
minimizing endangered species use of the site. Approximately 5 
acres in Ponds 2, 3, and 9 were deep ripped in order to increase 
soil permeability and to prevent any further puddle formation. 
About 800 cubic yards of earth fill material was added to a 1- 
acre area of Pond 3 where persistent puddles formed during the 
winter of 1988-1989. 

A 4-acre area in Pond 9 was disced to discourage nesting use by 
snowy plovers. Also, research into effective long-term 
dissipation and management techniques for the remaining selenium 
inventory and monitoring of impacts continued. 

CURRENT CONDITIONS AT KESTERSON RESERVOIR 

Ground Water 

Reclamation currently samples 27 shallow water quality monitoring 
wells and 41 pollutant plume monitoring wells at and adjacent to 
Kesterson Reservoir. This monitoring is done on a quarterly 
basis, as specified in the Central Valley Regional Water Quality 
Control Board's Monitoring and Reporting Program No. 87-149. The 
monitoring program was developed in collaboration with the 
Regional Board to detect and monitor migration of selenium and 
other constituents under and downgradient of Kesterson Reservoir. 
Results from this monitoring program have confirmed that the 
extent of selenium migration into the aquifer has been minimal 
and that the several small plumes of seleniferous drainwater 
detected between 1984 and 1986 have now all but disappeared. 

At present, only four wells exceed the designated "plume 
detection level" of 10 ppb selenium, compared to about 30 wells 
in the period from 1984-1986. Selenium concentrations in these 
four wells range from 11 to 40 ppb. The rapid decline in 
selenium concentrations detected after delivery of agricultural 
drainage water ceased in 1986 is consistent with research 
findings that naturally occurring geochemical/microbial processes 
transform and immobilize soluble selenium in the shallow aquifer 
underlying the Kesterson Reservoir area. 

The agricultural tile drainage water discharged into Kesterson 
Reservoir also contained elevated levels of salts and boron. 
Unlike selenium, these constituents moved freely into the aquifer 
and remain mobile in this environment. The residual plume 
extends from several feet to about 140-feet below the ground 
surface with an estimated average depth of about 60-feet. 
Ground-water samples from water quality monitoring wells adjacent 
to the northeast border of the Reservoir indicate that this plume 
is confined to a band that extends no more than 1,000 feet from 



the Reservoir in this direction. Water quality samples to the 
east of the Reservoir, adjacent to Kesterson Ponds 1, 2, and 5, 
are limited; however, geophysical measurements of soil 
conductivity have indicated that the plume of high total 
dissolved solids (TDS) does not extend more than 1,200 feet from 
the edge of the Reservoir in the easterly direction. 

Surface Water 

Ephemeral pools formed by rising ground water have not occurred 
at Kesterson Reservoir since the completion of filling. Although 
rainfall was below normal levels in 1988, 1989, and through 
February 1990, heavy rainfall events did occur during the winter 
of 1988 and 1989. After rainfall events greater than about 0.5 
inch, many shallow puddles formed on top of filled habitat. 
These puddles formed where there were slight depressions and 
where soils were heavily compacted by equipment during the 
filling operation. There has been no significant puddling in 
either the grassland or open habitats. Immediately after heavy 
rainfall events puddles were estimated to cover about 1 percent 
of the filled habitat. In a matter of days many puddles 
disappeared and persistant puddles (those lasting more than 1 
week) in 1988-1989 covered about 0.25 percent of the entire 
Reservoir. In the winter of 1988-1989 a few puddles persisted 
for weeks and usually overlapped later rainfall events. The 
largest of these puddles, found in Trisection 1, varied between 
0.25 and 0.35 acres in size. No persistent puddles have formed 
in these areas since they were deep ripped and filled. 

Reservoir-wide, the geometric mean selenium concentrations in 
rain puddles was 4.0 ppb (n = 53; range = <1 - 50). A general 
trend of decreasing selenium concentration from south to north 
was observed. This trend is similar to trends observed in the 
water extractable fraction of soil selenium. The highest 
concentrations were found in puddles in Pond 3. In late 
February, aquatic invertebrates were discovered in a group of 
puddles in Pond 3. The selenium concentration in these puddles 
ranged from 44 to 50 ppb. No vegetation was observed in these 
puddles, but widgeongrass seeds and signs of wildlife activity 
were observed around their edges. Seeds and aquatic beetles were 
collected for selenium analysis. Widgeongrass seeds^had a 
geometric mean selenium concentration of 622 ppm (n - 3; range - 
570 - 680). The aquatic beetles had a geometric mean selenium 
concentration of 15.3 ppm (n = 5; range = 13 - 19) which is 
comparable to levels found in terrestrial beetles collected 
during the 1989 sampling year. The area where these puddles 
formed were ripped and earth filled during the summer of 1989. 
These actions appear to have been successful as no significant 
puddles have formed in this area during the winter of 1989-1990. 

During the current 1989-1990 winter season, we have observed that 
some puddling continues to occur. We are monitoring puddles that 



form on a regular basis. Analysis of samples from these puddles 
has not yet been completed. 

Biota 

Three major habitat types presently exist at Kesterson Reservoir: 
filled areas covering about 710 acres; grassland areas covering 
about 400 acres; and open (disced former cattail) areas covering 
about 170 acres. A summary of selenium concentrations found in 
plants and invertebrates collected in 1988 and 1989 is in Tables 
1 and 2 . 

The filled area is covered primarily by annual plant species 
dominated by burning bush, clover, annual grasses, prickly 
lettuce and in some areas mustard. Mustard was only found in 
restricted areas in Trisection 2. The geometric mean selenium 
levels in plants collected from filled habitat is 2.9 ppm (n = 
103 ; range = 0.1 - 82 ) . 

The grassland areas are dominated by saltgrass and have been 
extensively sampled in the past. The geometric mean selenium 
concentration in all plants collected in 1988 and 1989 is 3.5 ppm 
(n = 96; range = 0.6 - 32). Sampling of plants and invertebrates 
has indicated that selenium levels are relatively low compared to 
selenium levels found in the aquatic habitats which formerly 
existed at the site. The geometric mean selenium concentration 
in all grassland plants sampled since August 1988, is 3.66 ppm (n 
= 455; range = 0.1 - 82). The geometric mean selenium 
concentration in all grassland invertebrates, excluding sowbugs , 
sampled since August 1988 is 7.7 ppm (n = 363; range = 0.1 - 78). 
Much higher selenium levels (geometric mean = 57 ppm, n = 54; 
range = 23 - 210) have been measured in sow bugs. These levels 
are apparently related to similarly high selenium levels in soil 
litter where sow bugs live and forage. High selenium levels in 
the soil litter are attributed to disposition of sediments and 
vegetation in the past when grassland areas were occasionally 
flooded with drainwater. The importance of the litter-sow bug 
food chain is unknown, but no sow bugs were found in the contents 
of the 54 bird and 148 small mammal stomachs examined to date. 

Open areas consist principally of disced cattail residue. These 
areas were not filled because they were above the target fill 
elevation, and were disced to eliminate tricolored blackbird 
habitat. As a result of discing, the organic sediment layer, 
which has elevated selenium levels, and cattail residue were 
mixed with underlying soil. A low growing groundcover, 
consisting of clover, prickly lettuce, burning bush, annual 
grasses, and other invader plant species, is colonizing this 
habitat type. Analysis of these plants show a geometric mean 
selenium concentration of 4.6 ppm (n = 112; range = 0.4 - 38). 
Invertebrate samples from this habitat type show an overall 



Table 1 

KESTERSON RESERVOIR 

1989 PLANT SELENIUM CONCENTRATIONS 

(ppm dry weight) 



DESCRIPTION 1 


N 1 


GEOMETRIC MEAN j 


RANGE 1 


GRASSLAND 


1 


alkali heath 


36 


3.8 


1.1 -32 


alkali weed 


18 


3.5 


0.9 - 8.5 


prickly lettuce 


18 


6.1 


1.2 - 20 


salt grass 


36 


2.7 


0.6 - 8.6 


salt grass seed 


18 


1.2 


0.2 - 4.7 










FILLED 1 


alkali heath 


15 


4.1 


0.4 - 28 


alkali weed 


24 


5.6 


1.0 - 29 


annual grass 


27 


1.3 


0.2 - 9.4 


annual grass seed 


18 


1.1 


0.2 - 7.0 


burning bush 


25 


2.8 


0.1 - 16 


clover 


17 


1.4 


0.2 - 13 


clover seed 


18 


2.2 


0.3 - 18 


mustard 


18 


14 


2.9 - 82 


mustard seed 


18 


4.8 


1.5 - 13 


prickly lettuce 


18 


4.3 


1.3 - 18 










OPEN 1 


alkali heath 


17 


2.6 


0.4 - 10 


alkali weed 


15 


2.4 


0.9 - 9.1 


annual grass 


17 


6.8 


1.2 - 38 


annual grass seed 


17 


6.1 


2.8 - 13 


burning bush 


36 


2.1 


0.3 - 16 


clover 


27 


8.4 


1.4 - 27 


clover seed 


18 


8.2 


2.9 - 25 


prickly lettuce 


36 


3.9 


0.6 - 16 



Table 2 

KESTERSON RESERVOIR 

1989 INVERTEBRATE SELENIUM CONCENTRATIONS 

(ppm dry weight) 



DESCRIPTION 


- N 


GEOMETRIC MEAN 


RANGE 1 


GRASSLAND | 


grasshoppers 


22 


4.2 


2.0 - 16 


beetles 


27 


13 


1.9 - 78 


crickets 


22 


6.9 


1.0 - 21 


sowbugs 


25 


58 


23-87 


mixed aerials 


30 


6.4 


2.0 - 18 


spiders 


19 


11 


2.0 - 40 










FILLED 1 


grasshoppers 


15 


3.1 


0.7 - 9.6 


beetles 


13 


8.1 


0.1 - 26 


crickets 


4 


4.8 


3.5 - 6.7 


sowbugs 


1 


32 




mixed aerials 


21 


3.8 


2.0 - 8.3 


spiders 


11 


9.9 


2.0 - 30 










OPEN 1 


grasshoppers 


18 


6.4 


2.0-25 


beetles 


19 


17 


8.3 - 41 


crickets 


15 


13 


6.3 - 23 


sowbugs 


7 


61 


32 - 120 


mixed aerials 


22 


5.8 


2.8 - 18 


spiders 


15 


14 


3.0-84 



geometric mean selenium concentration of 10 ppm (n = 81; range = 
2 - 61) . 

Bird use of the Reservoir has changed substantially. Drying and 
filling of the Reservoir has made the site unattractive to 
nesting tricolored blackbirds and the aquatic bird species in 
which impacts have been observed in the past. However, the 
Reservoir is presently being used by terrestrial bird species 
such as meadowlarks, horned larks, killdeer, and sparrows. Adult 
western meadowlarks were collected in 1988 and 1989. The 
geometric mean selenium level in livers of meadowlarks collected 
in 1989 was 16 ppm (n = 10; range = 4.8 - 36) and in livers from 
meadowlarks collected in 1988 the geometric mean was 23 ppm 
(n = 15; range 8.4 - 76). These levels are elevated when 
compared to liver selenium levels in meadowlarks collected from 
Volta in 1988 (4.1 ppm, n = 5; range = 3.3 - 4.7). Selenium 
concentrations in livers of other birds which are similar to 
these concentrations found in Kesterson Reservoir meadowlarks are 
known to have produced reproductive impairment. However, there 
are interspecific differences in how selenium affects birds. No 
abnormalities were found in any of the meadowlarks collected. 
All the meadowlarks appeared healthy, as determined by the 
condition of the integuments, internal organs and the amount of 
fat and muscle. Elevated selenium levels were found in 
meadowlark eggs collected in 1988 and 1989 (1988 geometric mean = 
23 ppm; n = 2; range =22-24 and 1989 geometric mean = 10 ppm; 
n = 5; range = 4.8 - 17). The geometric mean selenium 
concentrations in eggs collected in 1988 from other terrestrial 
bird species ranged from 1.7 ppm (n = 1) in mourning doves to 19 
ppm (n = 15; range = 7.6 -58) in killdeer. In 1989 geometric 
mean selenium concentrations ranged from 2.5 ppm (n = 2; range = 
1.3 - 4.7) in mourning doves to 6.6 ppm (n = 6; range 4.2 - 15) 
in killdeer. No selenium related embryotoxicity was found in 
terrestrial bird species observed during the 1988 and 1989 
nesting seasons. The last bird death apparently related to 
selenium toxicosis at the Reservoir was a dead coot salvaged on 
July 3, 1988. 

Results of analysis of small mammals collected at Kesterson 
beginning in February 1989 indicate that whole body selenium 
concentrations are not significantly different than those sampled 
in 1988, except deer mice which were significantly lower in 1989 
than in 1988. No adverse reproductive or growth impact to small 
mammals resulting from selenium has been observed at Kesterson 
Reservoir. Likewise, a study of raccoons in 1986 at the 
Reservoir found no adverse impacts from selenium. A 1986-1988 
study of the endangered San Joaquin kit fox found limited use of 
the Reservoir by this species and no negative effect of selenium 
levels at Kesterson Reservoir on kit fox. However, the upland 
habitat now present at Kesterson Reservoir has resulted in an 
environment that may be more attractive to the kit fox. Two of 
eleven coyotes collected within Kesterson Reservoir as part of 



the kit fox study had liver selenium levels within the range 
associated with selenium toxicosis in domestic dogs, and one of 
these two showed clinical signs associated with selenium 
toxicosis. The study also documented that small mammals 
accounted for 98 percent of the remains in kit fox scats 
collected from the Kesterson Reservoir area and 69 percent of the 
stomach contents of coyotes collected from the Reservoir. 
American coots were the second most important food item 
(28 percent) in the Kesterson Reservoir area coyote diet. 
Because of 1) the selenium accumulation observed in coyotes 
collected from Kesterson Reservoir, 2) continued elevated 
concentrations in small mammals, and 3) potentially better kit 
fox habitat produced by filling wetlands, kit fox use of the 
Reservoir continues to be monitored. 

1990 MANAGEMENT 

Selenium levels in some biota at Kesterson Reservoir continue to 
be elevated above background levels and above levels that have 
been observed to result in impacts in the presence of drainwater. 
This observation is tempered by the fact that no impacts related 
to selenium toxicosis have been observed in birds or mammals 
since the elimination of standing water and the completion of 
filling. Management activities at Kesterson Reservoir are 
therefore focused on activities that minimize exposure of 
wildlife to elevated levels of selenium and eliminate aquatic 
habitat, while continuing to monitor for impacts and to conduct 
research into long term selenium dissipation techniques. 

Grassland Areas 

Selenium levels in the saltgrass areas of the Reservoir are 
generally low and these are the most stable habitats. The 
vegetative cover assists in minimizing surface water and no 
puddling has been observed in these areas. Monitoring of biota 
and selenium levels will continue. No direct management actions 
are proposed for these areas at this time. 

Filled Areas 

Filled areas are becoming covered with a variety of plants that 
generally have low levels of selenium. Further plant cover will 
assist in minimizing the occurrence of puddles. Disturbance of 
the soil would disrupt this plant cover and also might tend to 
bring buried selenium to the surface. No direct management 
actions for the filled areas are therefore proposed, other than 
treatment of puddles as they occur. 

Open Areas 

Approximately one-half of the open area habitat will be disced. 
The entire open area was disced at the time of the filling 



9 

operation in order to eliminate standing cattails. Since that 
time the open habitat has become re-vegetated with clover, 
prickly lettuce, burning bush, annual grasses, and other invading 
plant species. The open areas tend to have higher selenium 
levels than other Reservoir habitats and, although no adverse 
impacts on wildlife have yet been observed, discing will be done 
on about one-half of the open area in order to evaluate its 
effectiveness in minimizing or eliminating potential 
contamination pathways. All of the open habitat is not being 
disced in order to observe succession in the plant community and 
to determine if open habitat will remain safe without ongoing 
management . 

Surface Water 

Rainwater puddle monitoring data from 1989-1990 will be evaluated 
and any areas where persistent rainwater puddles may form in the 
winter of 1989-1990 will be disced, deep-ripped and/or filled. 

There remains continuing uncertainty as to conditions at the 
Reservoir in the event of an unusually wet year. In a wet year 
there is the potential that extensive surface water could occur 
at the Reservoir as well as on surrounding lands. However, since 
the Reservoir is still enclosed by dikes, there is no surface 
outlet for water at the Reservoir. It is therefore conceivable 
that while surrounding lands drain, surface water at the 
Reservoir could slowly evaporate and infiltrate, concentrating 
constituents and providing attractive habitat for shorebirds and 
other species during the spring months when such conditions would 
be particularly undesirable. In such an event, current 
management options would include intensive hazing and/or 
sterilization of the areas. Another option may be to avoid such 
conditions by restoring natural drainage conditions at the site. 
This will of course require careful consideration of the 
advantages and disadvantages of such an action. We intend to 
explore, in consultation with Regional Board staff, a contingency 
surface drainage plan that could be implemented in anticipation 
of or in the event of unusually wet conditions. 

Mo nitoring 

An intensive monitoring program is ongoing at Kesterson Reservoir 
and will be continued. Monitoring of water quality and biota is 
designed to detect any adverse effects from contamination at 
Kesterson Reservoir as well as any migration of contaminants 
offsite. Reclamation will continue to provide the results of its 
monitoring routinely to the California Regional Water Quality 
Control Board - Central Valley Region, as specified in Monitoring 
and Reporting Program No. 87-149. Since dewatering of the 
Reservoir and filling of ephemeral pools, the emphasis of the 
biological monitoring has shifted to detection of any adverse 
effects to wildlife associated with the dry habitats now present 



10 

at Kesterson Reservoir. Continued emphasis will be placed on 
this effort to verify the lack of impacts associated with the dry 
land habitats. In addition, we are routinely monitoring any 
surface puddles that form at the Reservoir and in the event of 
heavy rainfall resulting in significant surface water at the 
Reservoir, more intensive monitoring will be implemented in order 
to rapidly identify any potential aquatic exposure pathways. 

Research 

Research activities aimed at identifying mechanisms for removal 
of selenium from soils will continue. Research activities are 
focused on two different management strategies including (1) 
management actions that optimize removal of selenium from surface 
soils (top 6 inches) through microbial volatilization and (2) 
management actions that remove selenium from the entire profile 
by a combination of plant uptake, plant volatilization, and 
microbial volatilization. The two major field scale experiments 
addressing these management options will continue. In addition, 
due to the continuing promise demonstrated by the microbial 
volatilization experiments in Pond 4 and with San Luis Drain 
sediments, a pilot project of microbial volatilization will begin 
in an open area of Pond 2. The pilot project will be carried out 
in a 2-acre test plot. A combination of irrigation and tillage 
will be used to stimulate microbial volatilization of selenium. 
Irrigation rates and tillage frequency will be geared towards 
what would be practical for large scale implementation at the 
Reservoir . 

In addition to research activities aimed at identifying 
dissipative processes, ongoing research aimed at evaluating a no- 
action management alternative will continue. These 
investigations, in conjunction with the intensive biological and 
ground-water monitoring programs, provide information on the 
behavior of selenium in this environment and the risks or lack 
thereof to ground water, surface water, and biota.